1. Field of the Invention
The present invention is directed to cyanoacrylate-based compositions, which include, in addition to the cyanoacrylate component, a thermal-resistance conferring agent, such as an alkylating agent and/or silylating agent, which provides reaction products of the compositions with improved thermal resistance properties.
2. Brief Description of Related Technology
Cyanoacrylates generally are quick-setting materials which cure to clear, hard glassy resins, useful as sealants, coatings, and particularly adhesives for bonding together a variety of substrates [see e.g., H. V. Coover, D. W. Dreifus and J. T. O'Connor, "Cyanoacrylate Adhesives" in Handbook of Adhesives, 27, 463-77, I. Skeist, ed., Van Nostrand Reinhold, New York, 3rd ed. (1990)].
A well-known problem of polymerized cyanoacrylates is their susceptibility to thermal degradation under elevated temperature conditions. [see e.g., G. H. Millet, "Cyanoacrylate Adhesives" in Structure Adhesives: Chemistry and Technology, 249-303, 279-80, S. R. Hartshorn, ed., Plenum Press, New York (1986)]. Due at least in part to this inherent limitation of the cured cyanoacrylate, the instant adhesive benefits of cyanoacrylate monomers have not been available in many applications where the bonded substrates may be exposed to temperatures exceeding 120.degree. C. on an intermittent basis, or extended exposure to temperatures of about 80.degree. C.
While this problem is distinct from stabilizing cyanoacrylate monomer formulations against premature polymerization, to preserve the instant adhesive benefits of cyanoacrylates strides toward improved polymerized cyanoacrylate thermal stability should not significantly degrade the storage stability or cure speed of cyanoacrylate monomer formulations from which the polymer is derived.
Efforts have been and continue to be made to improve the thermal stability of cyanoacrylate adhesive bonds.
For instance, in U.S. Pat. No. 3,832,334, the addition of maleic anhydride is said to produce adhesives which have increased thermal resistance while preserving fast cure speed of the cyanoacrylate adhesive.
In U.S. Pat. No. 4,196,271, tri-, tetra- and higher carboxylic acids of these anhydrides are said to be useful for improving heat resistance of cured cyanoacrylate adhesives.
U.S. Pat. No. 4,450,265 is directed to the use of phthalic anhydride to improve heat resistance of cyanoacrylate adhesive bonds.
U.S. Pat. No. 4,532,293 refers to benzophenonetetracarboxylic acid (or its anhydride) to provide a superior heat resistance for cyanoacrylate adhesives.
According to Chem. Abst. 85:64138p, a cyanoacrylate adhesive which includes a graft copolymer of methyl methacrylate and a fluorine containing rubber as a plasticizer is reported to give improved stability to thermal shocks.
In U.S. Pat. No. 4,490,515, cyanoacrylate compounds containing certain maleimide or nadimide compounds are reported to improve the hot strength properties of cyanoacrylate adhesives.
In Japanese Patent Document JP 55/66980, mixtures of certain sulfone compounds and a dicarboxylic acid or dicarboxylic anhydride are reported, which are said to improve heat resistance of cyanoacrylate adhesives.
In Japanese Patent Document JP 48/8732, cyanoacrylates containing 3-25% divinyl sulfone are reported to have improved heat resistance.
In U.S. Pat. No. 5,306,752 (Attarwala), U.S. Pat. No. 5,328,944 (Attarwala), U.S. Pat. No. 5,288,794 (Attarwala), and U.S. Pat. No. 5,424,343 (Attarwala), a cyanoacrylate-containing composition is provided which is stabilized against thermal degradation by the addition of certain quinoid compounds, certain sulfur compounds, certain mono, poly and/or hetero aromatic compounds, and napthasultone compounds, respectively.
And U.S. Pat. No. 4,440,910 (O'Connor) refers to cyanoacrylate compositions, which include certain elastomeric acrylic rubbers to give improved properties, particularly after exposure to elevated temperatures.
Notwithstanding the state-of-the-art, there continues to be a need to identify materials which will improve the heat performance of cyanoacrylate adhesives so as to increase the options available to accomplish this goal, particularly depending on the desires in the marketplace, and/or provide further improvements over the existing additives known to enhance cyanoacrylate thermal resistance.